This application is generally related to pipelined converters such as are used in pipelined analog to digital converters (ADCs).
Analog-to-digital converters are employed in a variety of electronic systems including computer modems, wireless telephones, satellite receivers, process control systems, etc. For such systems, it is desirable to employ cost-effective ADCs that efficiently convert an analog input signal to a digital output signal, over a wide range of frequencies and signal magnitudes, with minimal noise and distortion.
An ADC typically converts an analog signal to a digital signal by sampling the analog signal at pre-determined sampling intervals and generating a sequence of binary numbers via a quantizer. A resultant sequence of binary numbers is a digital representation of the sampled analog signal. Some commonly used types of ADCs include integrating ADCs, Flash ADCs, pipelined ADCs, successive approximation register ADCs, Delta-Sigma ADCs, two-step ADCs, etc. Pipelined ADCs and Delta-Sigma ADCs are currently popular in applications requiring higher resolutions.
A pipelined ADC circuit samples an analog input signal using a sample-and-hold circuit to hold the input signal steady and a first stage ADC to quantize the input signal. The first stage ADC then feeds the quantized signal to a digital-to-analog converter (DAC). The pipelined ADC circuit subtracts the output of the DAC from the analog input signal to produce a residue signal of the first stage. The residue signal is passed as the input to the next stage. A similar set of operations is performed in the subsequent stages of the ADC.